Condenser-discharge electric



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H. E. EDGERTON CONDENSER-DISCHARGE ELECTRIC SYSTEM Ongmal Flled Dec 6 1941 March 6, 1945.

Reiaued Mar. 6, 1945 Harold E. Edgerton, Belmont, Mass.

Original No. 2,351,603, dated June 20, 1944, Serial No. 421,931, December 6, 1941. Application for reissue December 8, 1944, Serial No. 567,134

25 Claims. (Cl. 315-241) The present invention relates to electric systems, and more particularly to condenser-charglng-and-discharging systems.

A system now in common use for flash-producing and similar purposes comprises a condenser charged from a source of direct-current energy and the charge of which is thereupon dissipated in a discharge circuit comprising a gaseous-discharge device, like a flash-lamp; The

resulting flash may, for example, be used in flash-photography.

It is frequently desired, however, in order to obtain improved lighting effects, to flash the object to be photographed from several directions at one and the same time. This, of course, requires a plurality of flash-lamps. When it is attempted to connect two or more such gaseousdischarge devices in parallel to the condenser, however, it is found that the condenser will dis: charge through only one of them, the other or others remaining inert.

It is accordingly an object of the present invention to provide for discharging the condenser simultaneously through a plurality of discharge devices connected in parallel to the condenser.

As study has disclosed that the reason for the failure of the condenser to discharge through more than one parallelly connected gaseous-discharge device is the relatively low resistance of the gaseous-discharge devices, a further object is to provide an electric system of the abovedescribed character in which the parallelly connected gaseous-discharge devices have resistances Other and further objects will be explained hereinafter and will be particularly pointed out in the appended claims.

The invention will now be described in connection with the accompanying drawing, in which Fig. 1 is a longitudinal section of a preferred gaseous-discharge device a plurality of which may be connected in parallel across a discharge condenser in accordance with thepresent invenof the arrows; Fig. 3 is a voltage-current chartion; Fig. 2 is a transverse section taken upon the line 2-2 of Fig. 1, looking in the direction acteristic curve of the gaseous-discharge device illustrated in Figs. 1 and 2; and Fig. 4 is a diagrammatic view of circuits and apparatus embodying the present invention.

The lower portion oi. the curve of Fig. 3 from the point B to the point C represents a positive voltage-current characteristic, such as may be obtained'in a cathode-ray oscillograph with a gaseous-discharge device l8 such as shown in Figs. 1 and 2. The axis of abscissae represents current, I, and the axis of ordinates, voltage, E. Initially, at zero current, the .voltage across the anode I and the cathode 9 of the gaseous-discharge flash-lamp device i8 may be about 2000 volts, as represented by the ordinate of the point A. When the hereinafter-described trip circuit is energized to effect a discharge of a condenser ll through the gaseous-discharge device ll, between the cathode 9 and the anode'l, the voltampere characteristic progresses very rapidly along the upper portion of the curve of Fig. 3,

sufficiently high to enable the voltage from the charged condenser to become stored up in each discharge circuit long enough to enable it to operate also on the other discharge circuits. when the condenser discharges through one of the gaseous-discharge devices, therefore, it will discharge also through the other gaseous-discharge devices. It is found that gaseous-discharge devices having positive voltage-current characteristic curves have sufiiciently high resistance for the purpose in hand.

With these ends in view. a feature of the invention resides in connecting a single condenser through a single impedance to a source of directcurrent energy to charge the condenser from the source, and connecting the condenser to a plurality of discharge devices of the above-dc.- scribed character, so as to effect discharge of the condenser simultaneously through the discharge devices. The discharge circuits are thus connected in parallel to the same single condenser, without any separating impedances.

from the point A to the point B, until the current, at the point B, attains a maximum value of about 500 amperes. Thereafter the current through the tube It drops, as indicated by the lower portion of the curve of Fig. 3, from the point B to the point C, until the current again drops to zero, as represented by the point C. At this time, the voltage, as shown by the ordinate of the point C, in Fig. 3 is relatively small, compared to the voltage represented by the ordinate of the point'A. Depending upon the tube It and circuit conditions, this final voltage, represented by the ordinate of the point C, may even be negative. The upper portion of this characteristic, between the points A and B, is shown constituted of long dashes, and the lower part, between the points B and C, of short dashes. If these dashes, long and short, respectively. .be regarded as representing time intervals or corresponding duration, the upper portion AB of the curve will be seen to be traversed in about onethird the time that the lower-portion BC 01' the is less than one-tenth of that for the portion 8 to C.

The resistance of the device It may be defined as the ratio of the voltage across its cathode I curve istraversed. Usually, the time required for the traverse of the portion A to B the curve gering circuit comprising a normally ineffective,

1 because non-conducting, gaseous-discharge trigand its anode l at the time when the current is of a maximum value. From the curve of Fig. 3, it appears that the voltage is about 1500 at the time, represented by the point B, when the curpoint a to the point 0. is such that sumclent voltage remains across the hereinafter-describedcircuit, at the point B, so that other tubes ll and 20, etc., in parallel with the tube II, will have sumclent voltage across them to become ionized, even if the first tube II should start a few microseconds before the others. If the tubes have short lengths, with large cross sections, at low gas pressure, the point B on their characteristic will be reached quickly, and it will have. so low. a value that parallel-connected tubes will not flash, even if ionized by the herein-described starter elec; trode H. The minimum value of the voltage corresponding to the point B for parallel operation is found to be in the range of voltage from 200 to 500 volts. H

Higher-resistance gaseous-discharge devices It are particularly useful for connecting into parallel with the condenser II, as hereinafter described. Lower-resistance gaseous-discharge devices, having characteristics the upper portions AB of which are steeper than illustrated in Fig. 3, cannot be employed in this way.

The gaseous-discharge device ll may be of the type disclosed in Letters Patent 2,277,698, granted March 31, 1942, to Kenneth J. Germeshausen, or an application of the said Germeshausen, Serial No. 418,403, filed November 8, 1941. It is shown disposed within an elongated, light-permeable glass-bulb protective jacket or envelope 28, which is shown mounted in a reflector It may contain krypton, xenon or any other suitable gas. The glass bulb 28 is cemented to a fiat insulatmg base plug 94, provided with three plug-in pin terminals 6, l2 and I 4 for connecting the gaseousdischarge device ll into circuit. Other gaseousdischarge devices may, of course, also be emger tube I. The trigger tube is shown connectedto terminals II and it across an impedance ll, illustrated as a bleeder resistor, so as to be supplied with-voltage therefrom. The bleeder resistor is connected in series with a bleeder resister 0* across the condenser II, which thus, by supplying energy to the bleeder'resistor 8|, constltutes the main powersupply for the tube l.

The tube I may, if desired, be of the coldcathode gaseous-discharge type illustrated and described in Letters Patent 2,185,189, 1,201,166 and 2,201,167, issued to Kenneth J. Germeshausen, on January 2, 1940, and May 21, 1940.

4 It may comprise an evacuated glass envelope containing several electrodes, namely, a solid cathode 2, an anode or plate 5, and one or more. grids, inner and outer grids being shown at I and 4, between the anode I and the cathode 2. As explained in the said Letters Patent,the source of the electrons is a bright cathode spot on the surface of the cathode 2. Part of the impedance II is shown connected between the cathode 2 and the grid 4, and a further impedance (not shown) may, if desired, be connected between the cathode 2 and the. grid 3. l I

A trigger-discharge circuit for a tripping condenser tl is also connected to the terminals l3 and It, in parallel with the tube I. One side of the condenser 4| is connected in this discharge circuit to the terminal It. The other side of the condenser II is connected, by way of a conductor 9|, to the primary winding ll of a tripping transformer St and, by way or conductors 32 and 21, to the terminal IS. The condenser 4| is thus connected in this discharge circuit in series with .this primary winding 14. One side of the secondary winding 18 of the transformer 36 is grounded to the terminal l5 by way of the conductors 32 and 21. The other side of the secondary' winding 38 is connected through the terminal I to the trip electrode II. A return path is afi'orded by capacity coupling of the trip-wire electrode II to the flash-lamp it. The discharge circuit of thecondenser 4| thus contains the gaseous-discharge device l8 and the secondary winding a, which operates as an induction coil.

ployed in accordance with the present invention.

The gaseous-discharge device It is shown hell-- cally coiled, and provided at one end of the helix with a return center leg at the end of which the anode 'l is mounted, the cathode 0 being disposed at the other end of the helix. The anode I and the cathode 9 are respectively connected to the pin terminals 6 and I2. One end of the before-mentioned starter electrode ll, shown as a high-voltage spark trigger-wire or trip-wlre flashing electrode, is connected to the plug-in terminal It, and at its other end is mounted over a plurality of the coils or turns of the helicaltube gaseous-discharge device ll.

, One side of the condenser ii is shown conbe supplied with energy The condenser ll may be supplied with directcurrent energy from any desired source, such as a battery. If a suitable source of alternatingcurrent, such as the ordinary 110 volt, 60-cycle house mains is available, however, the condenser ll maybe connected thereto by plugging at H. The plug II is connected by input wires 13 to a jack I", which is connected byconductors I33 and vll'i to the primary winding of a transformer ll. The secondary winding 49 of the transformer 45 is connected to the condenser ll through a rectifier 12. The rectifier 12 may also from this alternatingcurrent source. To this end, its cathode 19 may be connected, by conductors ill and I23, in circuit with a winding 03 that may constitute a further secondary winding for the primary windlng 'll of the transformer l5.

A charging impedance, which may be constituted of resistance, or inductance, or both, may be connected in circuit between the condenser I I and the secondary winding 49. This is not illustrated. because not needed if the secondary winding It has a high impedance, for it may then perform, also, the current-limiting function of a separate charging resistor or other impedance.

one or two tubes.

In this manner not only the condenser I I, but, also. the condenser 4I becomes charged from the. same direct-current source 49, 12.

The tube I may be triggered, to initiate the discharge of the condenser II through the gaseous-discharge device, in any desired way, as byof additional gaseous-discharge lamp devices, two

of which are shown at I9 and 29. may be connected across the condenser II in parallel with the gaseous-discharge device I9. The pin terminals I2 of the gaseous-discharge devices II and 29 are shown connected to one side of the condenser II, in parallel with the corresponding pin At any time after the direct-current source 49,

12 charges the condenser I I to its maximum value, upon the closing of the automatically operating switch II, the potential of the grid 4 willbecome raised until the break-down voltage between the grid 4 and the cathode 2, or the grid 4 and the grid 9, is exceeded. The normally ineffective trigger tube thereupon becomes eflective by being rendered conducting. Current then flows through the trigger tube I, causing the condenser M, which had become charged from the directcurrent source 45, 12 simultaneously with the charging of the condenser I I to discharge through its before-described trigger-condenser-discharge circuit comprising the primary winding 14 oi the transformer 99. A resulting voltage-surge pulse 01' the secondary winding 99 of the transformer 99 becomes thus impressed upon the trigger electrode ll of the gaseous-discharge tube I9. This causes the gas in the gaseous-discharge tube I9 to ionize, producing a conducting path throughthe device I9, and permitting the condenser II to discharge therethrough. The resulting highvoltage triggering spark through the flash-lamp II will yield a very brilliant exposure flash of extremely short duration. As the time taken for the trigger tube I to trip the gaseous-discharge device I9, between the closing of the switch 5i and the flash of light from the device I9, is very brief, it is possible to produce this very brilliant flash or light for a very brief period of time. When the condenser II is fully discharged, the gaseousterminal I2 of the gaseous-discharge device II, by conductors 9 and 29. The pin terminal I2 of the gaseous-discharge device I9 is shown connected to the conductor 29 by a conductor 44, and the pin terminal 12 of the device 29 by a conductor 9|.

The terminals 9 of the gaseous-discharge devices I9 and 29 may, similarly, be connected, in parallel with the corresponding terminal I of the gaseous-discharge device I9, to the grounded terminal II at the other side of the condenser II. The connections may be traced from the grounded terminal I5, by way of conductors 21. and II, to a conductor 49 leading to the pin terminal 9 01 the gaseous-discharge device I9 and a conductor 92 leading to the pin terminal 9 of the gaseousdischarge device 29.

Separate, tripping condensers 42 and 43, corresponding to the condenser 4|, and separate tripping transformers 49 and 59, corresponding to the discharge device I9 extinguishes, and the cycle that of one lamp I9. The resulting flash is half as long, but also contains half as much light from each tube. Thetotal light is the same for both If the lamps I9, I9, etc., have difierent resistances, the output and the duration of each are calculated approximately as though the lamps were resistors, using Qhms law. The abov methods are applicable only when the energy per flash is enough thermally to ionize the gas in the lamps.. For the example shown, the tube may have dimensions as follows:

Inside diameter- 6 mm.

Length between electrodes 1 and 9=15 inches.

Gas=xenon-k rypton mixture at 7 cm. pressure transformer 39, are provided for the gaseous-discharge devices I9 and 29. The condenser 42 and the primary winding 41 of the transformer 49, and the condenser 43 and the primary winding 94 01' the transformer 96, are respectively seriesconnected in tripping condenser-discharge circuits, in parallel with the condenser 4 I. and the primary winding 14 of the transformer 36. The tripping condenser-discharge circuit for the gaseous-discharge device I9 may be traced from the terminal I3, through the condenser 42, by way of a conductor 92, through the primary winding 41 of the transformer 49, and by way of conductors 49, I9'

The tripand 21, to the grounded terminal I5. ping condenser-discharge circuit for the gaseousdischarge device 29 may be traced from the ter minal I9, through the condenser 43, by way of a conductor 93, through the primary winding 94 of the transformer 59, and by way of conductors 52, I6 and 21, to the terminal I5.

The secondary winding 49 of the transformer 49 is connected to the pin terminal I4 of the gaseous-discharge device I9 and the grounded terminal I5 by way of the conductors 40, I8 and 21, and the secondary winding 55 of the transformer 59 is connected to the pin terminal I4 of the gaseous-discharge device 29 and the grounded terminal I5 by way of conductors 52, I6 and 21, in a manner similar to the connection of the I secondary winding 38 of the transformer 39 to the By reason of the fact that the resistances of the gaseous-discharge devices I8, I9 and 29 are suiilciently high, as depicted by the characteristic curve 01' Fig. 3. a discharge of the condenser II will take place through not one only of the gaseous-discharge devices I9, I9 and 29, but simul taneously through all three of them. The total amount of energy discharged by the condenser I I into these three gaseous-discharge devices I9; I9 and 29 is, of course, approximately the same as that which would be discharged through a single gaseous-discharge device, if no more than a single gaseous-discharge device were connected to the condenser II. The energy discharged by the condenser II is the same, whether dissipated in one gaseous-discharge device or many It is frequently desirable, however, as before focus light upon the object to be photographed from different directions. According to the present invention this may be efiected by connecting in parallel to the condenser II, as illustrated, a

plurality of flash -lamps l8, l9 and 20, each having a positive voltage-current characteristic, as illustrated in Fig. 3, and providing only a single current-limiting impedance for the condenser H, which may be embodied in the secondary winding ID, or which may be constituted of a separate charging resistor or other impedance (not shown) connected between the secondary winding 49 and the condenser Ii. Ii. the voltage across the condenser li supplied by the secondary winding 48 and the rectifier i2 is, say, 2000 volts, the maximum current supplied by the condenser ll may be in the neighborhood of '500 amperes, as illustrated in Fig. 3, and the resistors 8| and 82 may be so proportioned that a desired voltage of, say, 300 volts shall appear across the terminals [3 and I! of the resistor 8|.

Modifications will occur to persons skilled in the art and all such are considered to fall within the scope and spirit of the invention.

What is claimed is:

1. An electric system having, in combination,

"a condenser, means for charging the condenser, a plurality of gaseous-discharge devices, means for connecting the gaseous-discharge devices in parallel to the condenser, a plurality of triggering circuits, one connected to each of the gaseous-discharge devices, and means for simultane-' ther discharge device, and means controlled by- ,the further discharge device for controlling the triggering circuits to effect a discharge of the condenser through the gaseous-discharge devices, the gaseous-discharge devices having. resistances sufiiciently high so that when the condenser di'scharges through one of the gaseous-discharge devices it shall discharge simultaneously through the other gaseous-discharge device.

3. An electric system having, in combination, a condenser, a plurality of discharge circuits each having a gaseous-discharge device having a positive voltage-current characteristic curve, means for connecting the discharge circuits in parallel to the condenser, and a breaker circuit for efiecting a discharge of the condenser through the gaseous-discharge devices, the breaker circuit having a breaker contact member and a condenser connected in series therewith.

4. An electric system having, in combination, two terminals that may be connected to a source oi energy, a condenser that may be connected to the two terminals so as to .become charged from the source, a plurality of discharge circuits each connected to the terminals and; each having a gaseous-discharge device provided with a cathode and an anode respectively connected to the two terminals and a control electrode, a' trigger circuit connected between the anode and the control electrode 0! each discharge device. and means for simultaneously triggering the trigger circuits to effect simultaneous discharge of the condenser into the discharge circuits.

5. An electric system having, incombination, a .condenser, an impedance, means for connecting the condenser to a source oi' direct-current energy through the impedance to charge the condenser, a plurality of discharge circuits each having a gaseous-discharge device, means. for connecting the discharge circuits in parallel to the condenser without substantial separating impedance between the parallelly connected discharge circuits and the condenser, and means for effecting a discharge of the condenser simultaneously into the discharge circuits.

6. An electric system having, in combination, a condenser, an impedance, means for connecting the condenser to a source of direct-current energy through the impedance tocharge the condenser, a plurality of gaseous-discharge devices, means for connecting the gaseous-discharge devices to the condenser. without substantial separating impedance between the gaseous-discharge devices and the condenser, and means for eflecting a discharge of the condenser through the gaseousdischarge devices, the impedances oi the gaseousdischarge devices being sufficiently high so that when the condenser discharges through one of out substantial separating impedance between the gaseous-discharge devices and the condenser, triggering means, and means for triggering the triggering means to effect a discharge of the condenser simultaneously through the gaseous-discharge devices.

8. An electric system having, in combination,

a condenser, means for charging the condenser, a plurality of gaseous-discharge devices, means for connecting the gaseous-discharge devices directly in parallel to the condenser without substantial separating impedance between the gase ous-discharge devices and the condenser, and means for effecting a discharge of the condenser through the gaseous-discharge devices, the impedances of the gaseous-discharge devices being sufllciently high so that when the condenser discharges through one of the gaseous-discharge devices it shall discharge simultaneously through the other gaseous-discharge device or devices.

9. An electric system having, in combination,

a condenser, means for charging the condenser,

a plurality of gaseous-discharge devices each having a positive voltage-current characteristic curve, and meansfor connecting the gaseous discharge devices directly in-=parallel to the condenser without substantial separating impedance 7 between the gaseous-discharge devices and the condenser, and means for eflecting a discharge or the condenser through the gaseous-discharge devices. I

10. An electric system having, in combination, a condenser, means for charging the condenser, a plurality of discharge circuits each having a gaseous-discharge device, a plurality of tripping transformers, one for each discharge device, means for connecting each transformer to the corresponding discharge device, and means for simultaneously tripping the transformers to discharge the condenser into the discharge circuits.

11.- An electric system having, in combination, a condenser, means for' charging the condenser, a plurality of discharge circuits each having a gaseous-discharge device, means for connecting the discharge circuits in parallel to the condenser. a plurality of tripping condensers; one for each discharge device, means for connecting each tripping condenser to the corresponding discharge device, and means for simultaneously tripping the tripping condensers to effect a discharge of the first-named condenser simultaneously into the discharge circuits.

12. An electric system having, in combination,

' a condenser, means for charging the condenser,

a plurality of gaseous-discharge devices each provided with a normally unenergized starting charges through one of the gaseous-discharge devices it shall discharge simultaneously through the other gaseous-discharge device or devices.

17. An electric system having, in combination, a condenser, means for charging the condenser, a plurality of gaseous-discharge devices each provided with a cathode, an anode and a control 'electrode, means for connecting the gaseous-diselectrode, means for connecting the gaseous-discharge devices directly in parallel to the condenser without substantial separating impedance between the gaseous-discharge devices and the condenser, and means for simultaneously energizing the starting electrodes to discharge the con-denser simultaneously through the gaseousdischarge devices.

13. An electric system having, in combination, a condenser, means for charging the condenser, a plurality of gaseous-discharge devices, means for connecting the gaseous-discharge devices directly in parallel to the condenser without substantial separating impedance between the gaseous-discharge devices and the condenser, a tripping transformer connected with each discharge device, a tripping condenser connected with each transformer, and means for simultaneously tripping the tripping condensers tov trip the tripping transformers to effect a discharge of the firstnamed condenser through the gaseous-discharge devices, the gaseous-discharge devices having impedances sufliciently high so that when the first-named condenser discharges through one of the gaseous-discharge devices it shall discharge simultaneously through the other gasecue-discharge device or devices.-

14. An electric system having, in combination, a condenser, means for charging the condenser, a plurality of gaseous-discharge devices each having a positive voltage-current characteristic curve, means for connecting the gaseous-discharge devices directly in parallel to the condenser without substantial separating impedance between the gaseous-discharge devices and the condenser, and a breaker circuit for effecting a discharge of the condenser through the gaseousdischarge devices.

15. An electric system having, incombination, a condenser, an impedance. means for connecting the condenser to a source of direct-current energy through the impedance to charge the condenser,

' a plurality of discharge circuits, means for connecting the discharge circuits in parallel to the condenser without substantial separating impedance between the parallelly connected discharge circuits and the condenser to effect a discharge of the condenser simultaneously into the discharge circuits, and. a contact member for controlling the discharge of the condenser.

16. An electric system having, in combination, a condenser, an impedance, means for connecting the condenser to a source of direct-current energy charge devices directly in parallel to the condenser without substantial separating impedance between the gaseous-discharge devices and the condenser, a plurality of transformers, one for each gaseous-discharge device, and each having a primary winding and a secondary winding connected between the anode and the con- I trol electrode of the corresponding gaseous-discharge device, and means for simultaneously ondary windings to effect control over thecon trol electrodes, thereby to effect simultaneous discharge of vthe condenser through the gaseousdischarge devices.

18. An electric system having, in combination, a condenser, means for charging the condenser, a plurality of gaseous-discharge devices each provided with a cathode, an anode and a starting electrode, means for connecting the gaseous-discharge devices directly in parallel to the condenser without substantial separating impedance between the .gaseous-discharge devices and the condenser, a tripping condenser connected to each starting electrode. and means for simultaneously tripping the tripping condensers to energize the starting electrodes, thereby to effect simultaneous discharge of the first-named condenser through the gaseous-discharge devices.

19. An electric system having, in combination, a condenser, an impedance, means for'ccnnecting the condenser to a source of direct-current energy through the impedance to charge the condenser, a plurality of gaseous-discharge devices each having a positive voltage-current characteristic curve, means for connecting the gaseous-discharge devices in parallel to the condenser without substantial separating impedance between the gaseous-discharge devices and the condenser, and a breaker circuit foreffecting a discharge of the condenser simultaneously through the gaseous-discharge devices, the breaker circuit having a breaker contact member and a condenser connected in series therewith.

20. An electric system having, in combination.

, a condenser, an impedance, means for connecting the condenser to a source of direct-current devices and the condenser. a triggering circuitconnectedbetween the anode and the control electrode 01 each discharge device, and means for simultaneously triggering the triggering circuits to discharge the condenser into the dis- 5 charge circuits, the impedances of the gaseousdischarge devices being sufliciently high so that when the condenser discharges through one of the gaseous-discharge devices it shall discharge simultaneously through the other gaseous-dis- 10 charge device or devices.

21. An electric system-having, in combination, a condenser, an impedance, means for connecting the condenser to a source of direct-current energy through the impedance to charge the con- 15 denser, a plurality of gaseous-discharge devices each having a positive voltage-current characteristic curve and each having a cathode, an anode and a control electrode, means for connecting the discharge circuits in parallel to the go condenser, and means controlled by the control electrodes for eflecting a discharg of the condenser simultaneously through the gaseous-discharge devices.

22. An electric system having, in combination,

a condenser, an impedance, means for connecting the condenser to a source of direct-current energy through the impedance to charge the condenser, a plurality of discharge circuits each having a gaseous-discharge device capable of car- 30 rying large currents and having a positive voltage-current characteristic curve, means for connecting the discharge circuits in parallel to the condenser, and means for eflecting a discharge of the condenser through the gaseous-discharge devices. a

23. An electric system having, in combination,

a condenser, means for charging the condenser,

a plurality of gaseous-discharge devices, means.-

ior connecting the gaseous-discharge devices in parallel to the condenser, triggering means, and

means for triggering the triggering means to elect a discharge oi the condenser simultaneously through the gaseous-discharge devices.

24. An electric system having, in combination. a condenser, means for charging thecondenser, a plurality of gaseous-discharge devices,means for connecting the gaseous-discharge devices in parallel to the condenser, triggering means, and means for triggering the triggering means to eflect a discharge of the condenser through the gaseous-discharge devices, the impedances of the gaseous-discharge devices being sufllciently high so that when the condenser discharges through one of the gaseous-discha e devices it shall discharge simultaneously through the other gaseous-discharge device or devices.

25. An electric system having, in combination, a condenser, means for charging thecondenser. a plurality of gaseous-discharge devices each having a positive voltage-current characteristic curve, means for connecting the gaseous-discharge devices in parallel to the condenser, trig-.

gering means, and means for triggering the triggering means to effect a discharge '01 the condenser simultaneously through the gaseous-discharge devices.

HAROLD E. EDGER'ION. 

